1. Field of the Invention
This invention pertains to the field of reinforcements embedded in poured concrete structures and more specifically concerns a coupling for end-to-end splicing of steel reinforcement bars.
2. State of the Prior Art
Steel reinforcement bars, commonly known as rebars, have been in widespread use in the concrete construction industry and numerous devices have been developed for splicing such rebars end-to-end where longer lengths are required, or for tying together precast concrete structures.
The known devices include threaded joints achieved by an internally threaded coupling sleeve, and grout joints where a mortar filled sleeve holds together the ends of two rebars. Grout splice sleeves are exemplified by U.S. Pat. Nos. 3,552,787; 4,692,052; 3,540,763 and 4,627,212, all issued to Yee. The U.S. Pat. No. 3,540,763 to Yee discloses a sleeve which tapers from a maximum diameter at a central point to terminate in opposite open ends. Two holes in the sleeve near the ends allow injection of a hardening grout which sets around the ends of two rebars inserted into the opposite ends of the sleeve. The interior surface of the sleeve is circumferentially grooved to better grip the grout material, and the opposing tapers of the sleeve provide a wedge-type lock on the bars to make an end to end splice. The U.S. Pat. No. 4,627,212 to Yee discloses variations on the earlier splice sleeve, including a sleeve with a straight cylindrical portion joined to a portion of tapering diameter, both portions having internal ridges spaced along the sleeve, the ridges in the cylindrical portion being of increasing height towards the end of the sleeve, while the ridges in the tapering portion are of constant height. This sleeve has two grout ports through which grout is injected into the sleeve. An inlet port is on the cylindrical portion, while an outlet port is near the end of the tapering portion. The outlet port is of smaller cross section than the inlet port, somewhat restricting outflow of the grout to ensure filling of the sleeve.
It is also well known to make a rebar splice by threading the rebar ends and joining the threaded ends by means of an internally threaded coupling sleeve. In particular, U.S. Pat. No. 5,152,188, commonly owned with this application, discloses a three piece mechanical splice in which the threaded rebar ends have been upsized to a diameter greater than the nominal diameter of the rebar rod.
While both threaded couplings and grout sleeves have been developed, a need exists for a coupling device which combines the advantages of each splicing method. A threaded coupling is quick and easy to make, and with proper attention to fabrication of the coupling sleeve and the rebar threading, such joints can be strong and dependable. Grout splices, while more complicated in that they require injection of properly mixed mortar, are useful where the rebar cannot be rotated relative to the splice sleeve, as would be necessary for a threaded joint. Such a condition commonly occurs where two precast concrete elements are to be joined. Reinforcing bars embedded in such precast structures cannot be rotated in order to make a splice or joint. The problem can be solved by providing grout sleeves on one of the elements, so that the sleeves are secured and aligned to receive protruding rebar ends on the other precast element, and the joints are then fixed together by injecting into the sleeves a cementitious compound, such as mortar and grout compounds which are commercially available for this purpose, and which upon hardening prevents separation of the sleeves and rebar ends.